The ugly face of IPv6
OSPFv3 uses link local addressing a lot
link local addresses need to know the outgoing interface
addressing scope
e.g. fe80::20a:e4ff:fe23:e9a9%em0
128bit is insufficient to identify a host
struct in6_addr can not represent theses addresses correctly but struct in6_addr is used often in the socket API
big bug in the standard